Hi MarjaE,
A new Mac build with this Accessibility Feature added has now been posted since I had run into other problems in the Sigil-0.9.8 release binary for Mac.
Feel free to grab the latest release and we can show you how to set the environment variable to disable cursor blinking either each time you launch Sigil or more permanently by adding it to your .bash_profile file.
export SIGIL_DISABLE_CURSOR_BLINK=True
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